Acylated fibronectin: a new type of posttranslational modification of cellular fibronectin.

Human fibroblasts were labelled with either [35S]methionine or [3H]palmitate and analyzed for the presence of 35S- or 3H-labelled fibronectin by immunoprecipitation and SDS-polyacrylamide gel electrophoresis. The majority of 35S-labelled fibronectin was found in the extracellular matrix of cells which could be removed quantitatively by mild trypsin treatment. In contrast, 3H-labelled fibronectin was found in a trypsin-resistant form. The 3H label of fibronectin could be identified predominantly as [3H]palmitate by HLPC analysis. The fatty acids remained stably associated with fibronectin during extraction and electrophoresis, indicating a covalent linkage. These results demonstrate that a subset of fibronectin different from extracellular matrix fibronectin is modified by acylation.